The present invention generally relates to radio apparatuses and more particularly to a planar antenna formed on a circuit substrate and a radio apparatus having such a planar antenna.
Investigations are being made on a planar antenna formed integrally on a circuit substrate in relation to radar sets of millimeter wavelength band. On the other hand, such a planar antenna is also important in the field of radio astronomy.
Conventionally, high-performance antennas that use a waveguide have been used for the reception of millimeter wavelength band radio signals.
However, such an antenna that uses a waveguide forms a three-dimensional circuit of heavy weight, and raises the problem of high cost. In addition, such an antenna that uses a waveguide raises the problem that it cannot be coupled to a semiconductor integrated circuit device directly.
In view of the foregoing circumstances and situations, investigations are being made in relation to the radar apparatuses of millimeter wavelength band to provide a planar antenna capable of being formed on a circuit substrate by patterning a metal film.
Patent Reference 1 Japanese Laid-Open Patent Application 2001-320228 Official Gazette
Patent Reference 1 Japanese Laid-Open Patent Application 2000-307334 Official Gazette
Japanese Patent 3,462,959
Non-Patent Reference 1 2003 IEICE Abstract C-2-103